Railway train emergency alarm apparatus



Dec. 21, 194& o. GRONDAHL 2,456,871

RAILWAY TRAIN EMERGENCY ALARM APPARATUS Filed May 24, 1945 a H65 *3 cg N Q Q g I\ Q 1% N n 1 INVENTOR.

3 g E LcmflaG ondalzl. g Y

v E Q MSATTaRNEY.

Patented Dec. 21, 1948 RAILWAY TRAIN EMERGENCY ALARM APPARATUS Lars 0. Grondahl, Pittsburgh, Pa, assignor to The Union Switch & Signal Company, Swissvale, Pa., a corporation of Pennsylvania Application May 24, 1945, Serial No. 595,566

8 Claims. 1

My invention relates to railway train emergency alarm apparatus, and more particularly to apparatus to send out an emergency alarm through railway train communication equipment.

In the operation of railway trains, derailed cars, dragging equipment, and other circumstances create conditions that are more or less of a hazard to all trains in the vicinity. Many times these accidental hazards are observed by railway personnel at a wayside station and by crew members on trains other than of the train to which the danger impends. Under all of such circumstances it would be a point toward safety if all the trains in the vicinity of such a hazard can be given an emergency alarm so that the crews of all these trains can. be on the alert and each crew can take what steps are necessary to bring their train under full control. In other words, it is desirable to have some means through which an emergency alarm can be given without delay when a hazard occurs, such alarm being created through devices automatically actuated when the hazard occurs or created through a circuit controller to be actuated by railway personnel when the hazard is observed.

Accordingly, a feature of my invention is the provision of novel emergency alarm apparatus for use in the operation of railway trains.

Another feature of my invention is the provision of novel emergency alarm means for use with railway train communication equipment.

Other features, objects and advantages of my invention will appear as the specification progresses.

To attain the foregoing features, objects and advantages of my invention I provide novel apparatus through which an emergency alarm current will be sent out from wayside stations and from train carried stations to be picked up by the associated receiving apparatus of each such station. The sending of this alarm current is accomplished automatically through a controller actuated due to the occurrence of a given hazard or is accomplished in response to manual operation of a controller by a watchman, operator or train crew member when the hazard is observed. For example, on trains the automatic sending of the alarm current can. be effected through a controller actuated by a predetermined drop in the brake pipe pressure or by a high deceleration or by a hot journal bearing detector. At wayside points, automatic sending of the alarm current can be based on the operation of a controller actuated upon the occurrence of a landslide, burnt bridge, high water, misplaced switch or similar circumstance. At all Wayside stations andat all train carried stations there is provided a manually operable controller which when actuated causes the sending of the alarm current, and thus any railway employee at wayside stations or on trains can cause the sending of the alarm current. The alarm current is of a preselected characteristic to which the receiving apparatus at all stations responds in a special manner to create a predetermined alarm signal. When used with train communication equipment the alarm current is efiective to influence the receiving apparatus not only under its normal or non-communicating conditions, but also to break in on any conversation that is in progress so that under no circumstances is there a delay in. the display of the alarm signal.

I shall describe one form of apparatus embodying my invention, and shall then point out the novel features thereof in claims.

The accompanying drawing is a diagrammatic view showing one form of apparatus embodying my invention when used with train communication equipment of the carrier inductive type. It is to be understood that my invention is not limited in its use to this one type of train communication apparatus and the present application serves to illustrate the principle of the invention and the many places the apparatus is useful.

Referring to the drawing, the reference character CO designates a vehicle of a railway train, such as a locomotive or caboose of a freight train, and in the drawing a caboose is shown. This vehicle is provided with communication equipment for two-way telephone communication with remote stations. That is, the caboose CO is equipped with apparatus for telephone communication with the locomotive of the same train, with other trains in the vicinity and with Wayside stations. Each such train carried and wayside station would be provided with communication equipment similar to that disclosed in the drawing. The communication equipment may take different forms, and I shall assume for the present application that the communication equipment is similar to that disclosed in a copending application for Letters Patent of the United States, Serial No. 575,311, filed January 30, 1945, by Paul N. Bossart, for Railway train communication systems, and reference is made to this Bossart application. for a full description of the communication equipment. It is suflicient for the present application to point out that such communication equipment utilizes the track rails and paralleling conductors, such as line wires, as a medium for transmitting the current along the railway, each station equipment being electrically coupled to the transmitting circuit or medium. Each equipment includes transmitting apparatus and receiving apparatus which use 7 av modulated carrier, current,

the carrier being modulated by voicefrequencies for telephone purposes and modulated by a preselected frequency for calling purposes. To provide non-interference between different trains and break-in facilities two different' carrier frequencies are provided, and each carrier channel is further provided with an: individual, calling; frequency, and by way of illustrationcarriers of: frequencies fl and 2 may form a first andasec-n ond carrier channel, respectively, andaufirstand a second tone frequency may serve as the calling current for the channels fl and f2, respectively;

Each receiving apparatus is normally energized d; n t oned to r ceive thes lling. r nt. 1 either carrierchannel, the. received ;current-being demodulated andapplied toth loud-speaker Y to soundthe restrictivecallingtone; Furthermore,- when a telephone conversation isto be carried on through ,eitherchanneL; the loud-speaker is disconnected--froin thelchannel tobe used for telephoning. and the earphonesof a hand set are connectedthereto, but the: receiving apparatus during a conversation; remains conditioned to also pickup the calling currentsof the other channel and sound the corresponding tonein;v the loudspeaker as a break-in, such toneinforming-theconditionserving as anemergency,calling. That: is, this featureof sendingthe twovcalling currents alternately is used to call all trains within therange of theequipmenttoassure that-although, different trains may-be communicating-throughone or the other of the two channels,- all trains will be called by the emergency call. It is clear that in such instances sueh emergency calling could be utilized as an emergency alarm signal; by providing apparatus which-would control the transmitting apparatus-tosend the calling current alternately when a hazardous condition occurs. However, I preferably use-differenttone currents for an emergency-alarm, and in that way the emergency alarm is distinct from the usual.

calling of the communication system;

In the accompanying drawing only-such pore tions of the communication; equipment of the aforementioned Bossart application necessary for,

a full understanding of; my invention are shown,

and in thedrawing elements corresponding to like elements of the Bossart application are given the same reference characters.

The caboose is provided with a'source of power,

such as the usual 32 volt-carlightingsystem, the terminals of this source being designated B32 and N32; The, 32 volts of this source arerconverted into a voltage suitable for use with electron tubes of the apparatus through a'motor gen-.

erator MG, a motor Nil-of which is connected to,

terminals B32, and,;N32-;and-a generator ll of;

which suppliesa relatively-high voltage atutermipl ed ,to primary of an output-transformer 1T3,- the carrier beingof-the channel frequency]! or f2.according as thecontrolrelay 'is-released or' nals B400 and N400. The positive terminal B32 of the source and the negative terminal N400 of the generator are connected to a ground electrode 12. The caboose is also provided with a series of control relays and different controlling switches which will be referred to from time to time-as the-specificationprogresses The; transmitting apparatuspf the caboose comprises a transmitter TR, a voice frequency supply means, a calling current and emergency current supply means, an input transformer, an output transformer, and associated circuits.

The transmitter TB is shown in block form for the sake,ofsimplicitYSince its specific structure formsnopa-rtloi mypresent invention and it is sufiicientrto. pointout that it would include a carrier oscillator, a. modulator and a power amplifier, which devices may be similar to those disclosedin the previously mentioned Bossart application. The transmitter;TR is proportioned to supply two diiferent, carrienfrequencies,to;provide twodifferent carrier channels, and I shall assume, these carrier frequencies are; of-the frequencyjl andf2 tot-form, a-firstand a second carrier channel,, respectively. The, selection of the channel frequency is obtained through .a--,con-trol relay 50 the, arrangement being such thatewhen relay 504s released the transmitter is -.conditioned to supply thercarrier of the first channel frequency fl and whenrelay 50 is picked up, Closing front contact- 53,; the transmitter is,conditioned'rto suppl the carrier-of the second, channel frequency f2.

transformer is connected to theinput-sideof the transmitter TR through a reactanceZB; Consequently, the voice"frequency serves to, modulate the.carrierr and av carrier telephone, current is suppicked up..

V0 and secondary winding-1570f transformer- -'Tl serving as an inductor of an oscillating circuit,

associated with tube-V6,;the circuits of tube V0 ,being governed by control relays 11,49, 25 and; 50. Power-is appliedttotheplate circuitof tube-y V0 as "well as to r the :plate circuits of; the tubes of thertransmitter TR from generator 1 I through, front contact 24 of control relay 25 when that z, a relay is energizedin a, manner to, appear heroine after. An oscillating circuit ",DGtWOI'k for tube V0 is ,formcd by the :topterminal of winding 15 1 being connected 'throughiwire ,l l andgridzleaki unit 12 tor control ;grid:'l3of.,tube-Vi5;: cath:-. ode Mg oftube V6 being-:connectew to. an"

intermediate terminal; of; winding l5 through frontxcontact 8850f relay [9; plate 'lfi ofitube V0 being: connected; to. another intermediate terminal of winding a! 5 through 1 blocking 1 ca-.

'- pacitor 8] Land front xcontact' [0610f relay [9,

and a capacitor 86 :being lconnectedrbetween the grid and plate circuit leads throughfront contact" 8501? relay l9; Aniadditional capacitor'llfl is con Furthermore, a third through front :contact- 5410f control relay 11." It is clear from the foregoing descriptio'nthatwh'en relays l 0 and 25' are l pickedsupiand relays -5ll and I! are released, thewltube V0 is. supplied' withpower and is connected for it to function as an oscillator, the oscillations being of a frequency predetermined by the capacitors 8B and 90 in multiple and which frequency I shall refer to as being a first calling tone frequency. These oscillations are applied to the transmitter TR to modulate the first carrier channel frequency fl and a calling current of a first tone frequency appears in the winding 45 of output transformer T3. When relays l9, 25 and 52 are picked up and relay l! is released, the tube V6 functions as an oscillator the same as before and the oscillations are of a frequency predetermined by the capacitor 86, and I shall assume that these oscillations are of a second tone frequency. These oscillations are applied to the transmitter to modulate the second carrier channel frequency f2 and a calling current of the second tone frequency appears in winding 45 of output transformer T3. These two calling tones are those used in connection with the communication equipment. To effect the calling tones the several control relays may be controlled in a manner similar to that disclosed in the aforementioned Bossart application but such control circuits are omitted in order to not unduly complicate the drawing since the calling control circuits form no part of my present invention. In addition I provide two emergency alarm tones in the following manner. When relays I9, 25 and I! are picked up and relay 50 is released, capacitors 86, 90 and 52 in multiple are included in the oscillating circuit for tube V6 and oscillations of a first emergency alarm tone frequency are supplied to the transmitter for modulating the first channel carrier frequency fl and a first emergency alarm tone current appears at the output transformer T3. Again, when relays l9, ll, 25 and 50 are all picked up, capacitors 86 and 52 in multiple are included in the oscillating circuit of tube V6 and oscillations of a second emergency alarm tone frequency are applied to the transmitter to modulate the second channel frequency f2 and a second emergency alarm tone current appears at the output transformer.

A secondary winding 46 of output transformer T3 is connected to a sending loop circuit coupled to the transmitting circuit by being connected to the track rails through wheels 41 and 48 of the caboose, the connection to the wheels being preferably made through the journal bearings in the well-known manner. When relay 50 is released closing back contact 49, a preselected portion of winding 46 is connected to wheels 41 and 48 through wires I38 and I39 and a capacitor 5| is connected across the connection to condition the loop circuit for efficient transfer of energy of the first carrier frequency fl. When relay 50 is picked up closing front contacts 6i and 62, a different preselected portion of winding 46 and another capacitor 60 are included in the sending loop circuit for efficient transfer of energy of the second carrier frequency f2.

The calling and emergency alarm apparatus is conditioned through a control relay 16 to supply the two calling tones or the two emergency alarm tones in a cyclic manner as will be more fully explained hereinafter.

The receiving apparatus comprises two pick-up coils 92 and 93 and two complete receivers designated receiver Fl and receiver F2, respectively, coil 92 being connected to the input of receiver Fl and coil 93 being connected to the input of receiver F2. Pick-up coils 92 and 93 are mounted on the caboose for inductive coupling to the wayside transmitting medium which includes the track rails and paralleling conductor as explained hereinbefore. Each receiver Fl and F2 is shown conventionally because the specific construction of these devices forms no part of my present invention and each may be of any one of several arrangements, and it is sufficient for the present application to point out that receivers Fl and F2 are responsive to the channel carrier frequency fl and f2, respectively, and each receiver includes means to demodulate the respective carrier current.

The output sides of the receivers Fl and F2 are normally connected in multiple to a loudspeaker LS through a three-pole double-throw switch S2 and a hook switch Sl, hook switch Sl being of the usual form on which a standard hand set not shown is placed, and which hand set is part of the communication equipment. Specifically, when switch S2 is set to the left, that is, to the position illustrated in the drawing, and the hand set is on the hook switch, the receiver Fl is connected to the loud-speaker LS through contact blade 99 of switch s2 and normally closed contact Bl of hook switch Si; and the output of receiver F2 is connected to the loud-speaker through contact blade ll2 of switch S2. When switch S2 is set to the right, contact blade 99 and contact 91 of the hook switch are included in the connection of receiver F2 and contact blade I02 is included in the connection of receiver Fl. The earphone of the hand set is connected to normally open contact Hi3 of the hook switch and thus when the hand set is removed from the hook switch the loud-speaker is disconnected from either receiver Fl or F2 according to the position of switch S2, and the earphone of the hand set is connected to that receiver for telephone purposes. The loud-speaker remains connected to the receiver not being used for telephoning.

It should be noted that the switch S2 also serves as a channel selector for selecting the channel frequency. The switch s2 when set to the left prepares the circuit for control relay 50 which selects the channel frequency of transmitter TR, such circuit extending from terminal B32 through ground, winding of relay 5B, transfer contact H5 and front contact N8 of continuity transfer contact of relay l6, and contact blade l l l of switch S2 to terminal N32; and when switch S2 is set to the right a circuit is formed from terminal B32 through ground, winding of relay 50, transfer contact H5 and back contact N4 of relay l6 and contact blade lll to terminal N32. Consequently, when switch S2 is set to the left the relay 5D is normally released and the transmitter TR supplies channel frequency fl and when switch S2 is set to the right relay 5!] is normally energized and the transmitter con ditioned to supply channel frequency f2. It is clear, however, that relay l6 controls through its contacts H4, H5 and M8 the control relay 50 and in turn thus controls the carrier channel frequency as will be more fully explained shortly.

The caboose is further provided with appara-' tus for governing the emergency alarm means automatically and manually. The first automatic switching means includes a pneumatic switch PS and a relay 30. The pneumatic switch PS is shown conventionally and includes a flexible diaphragm 3l mounted in a reservoir 32. The chamber of reservoir 32 to one side of the diaphragm St is connected through pipe 33 to the auxiliary reservoir of the brake equipment on the caboose CO, and the chamber of the reservoir answere 32 th theother side of the diaphragm is connected throughplate 3 i' to th'e' brake pipe on" the caboose; The: arrangement is' such that with equ'al p'res suresxon ea chside of the diaphragm -S-Pand in fact when thei'brake pipe pressureis reducedfor servi'ce application of the train" brakes, .a contact member 3-5: which is 'operatively connected' -with di'aphr'a'gm 3 l is in engagement with fixed con tacts 35%and 3Tto complete the connection therethroughgbutwh'en a large reduction in'brake pipe pressure occurs, such as occurs-when an emer gency brake application is made, the contact" member 35 is moved far enough by diaphragm tl tofldisengage contacts 35 and 3?. Relay 30 is normally energized through a stickcircuit which includes contact 35, this circuit being traced from terminal B32 through ground, lground electrode 381' front contact 39 and Winding of relay 3!), and contact 35 of the device PS to terminal N32. Relay: 30 once released by the opening of contact 35 rem'ains released although the contact 3'5 is reclosed, until'such time as a pick-up circuit is closed through spring return type push button PB as Will be'readily' understood by an inspection of the drawing. Relay 30 when released to close backcontacts to; H, 62 and 113 governs control relays ll, 19, and it to control the emergency. alarm means in a-rnanner to appear shortly. 1

A'Esecond'automatic means on the caboose'in eludes an axle driven generator 55 and'relays 56tand5'l. Generator 55 is preferablya direct current generator connected to an axle of the caboose through a drive mechanism indicated conventionally by a dotted line 58. The terminals of generator 55 are connected across the Winding of relay 5% through a capacitor 59; Thus capacitor 59'serves to block the flow of direct current from the generator 55 as long as the voltage of the generator is substantially constant, but a sudden change'in the voltage would cause a'current impulse to be applied'to the relay. The parts are proportioned so that therelatively high deceleration in the rate of rotation of the axle ofthe caboose caused by an emergency brake application or some other predetermined brake application creates'a change of voltageof gen erator 55 that results in a current impulsewhich" energizes relay 56 sufiiciently to pick up the'relay. and open back contact 6 Relay 5'l is normally? retained energized through a stick circuit-in cludingterminal B32; ground electrode 65; front contact Biiand Winding of relay 5? and backcontact 64 of relay. 5E5 to terminal N32. Relay 5'! once released can be reset through a pick-up circuitthat'includes push button PBl. Relay 5!- governs at its back contacts 61, 68, 69 and 82 the control relays ll, i9, 25 and H5, and in turn the emergency alarm means, as will bepointed out shortly,

A manually operable switch EM is provided with contacts 26, 2'5, 28' and 29 to also control-the several control relays and in turn the emergency alarm'means, as will also be described presently.

Normally each receiver Fl and F2 is active, the transmitter TB is deenergized and the several control relays and switches occupy the positions shown in the drawing. With the train operating. under normal conditions the equipment can be used for telephone communication in the usual manner. In the event danger impends and an emergency application of the train brakes is made, such brakepipe reduction will actuate device PS to open contact 35 and deenergize relay 30, and relay 3l'ireleases and remains released until such time as its pick-up circuit is'clo'sed through push button PB. With relay 3!] releasedclos'ingback frbnt contact 2% and apply power to tube V6 and to' the transmitterTR'; The closin'g of'back circui-t of--' tube "V6 The 01 usingof back Contact 413 of relay- 39 completes a simple circuit for relay" H and that relayis" picked upso' that '10 Y capacitor 52is'-included in" the oscillatin'gicircuit' rel ayltilcompletes a' circuit'for'r'elayw, this sir cuit ext'endingsfrom terminal B32 through ground, bachconta'ct l35 and windin'gi'of relay l5 and back 'contaot' lli' of relay to terminal N323 Relay'lt' bein'g thus controlled throughits own b'a'ck contact "I the relay; is operated at a rate predetern-i'inedby the constru'ction'of'the relay and byb thecapacitor' connected across "the wind m of the relay. Such cperation'of relay 16 causescontrol relayf'5ll' to be alternately picked up-andrelease'd. E-a'ch period th-at relay 59 is we released; carrier current of the first channel ire quency" fl' modulated by the'first emergency cal-arm tone irequencyis suppliedto" the transmitting circuit and each period relay 5E3 is picked up;'-carrier'- current of thesecon'd channel frequency f2 modulated by the second emergency alarmfrequencyv is suppliedto" the transmitting gcircuit. These two emergency'alarm currents will be alternately supplied as long as relay 30 remains released;

Such emergency *alarm "current will be picked uprby the receiving apparatus-of" each nearby 5 station and-the emergency-alarm sounded at the loud-speaker of each such station; That is'to say, when an emergency" brake application isma'de on the'train of which cabooseCO is a part,

an eniergency alarmsignal is provided for nearby -trains, such'emergency alarm serving as a step towardsafety; due to the-factthat the hazard for which the emergency brakeapplication was made ma'y be a hazard for other'trains. an' emergency brake application of a train' may s cause derailment of a--car' of the train which would-become a hazard for anytrain-on adjacent tracks H In- 'theevent relay-56 is picked up-by-acurrent impulsefrom' generator 55 duetoa predetermined ,1 deceleration of the traingrelay 5i is in turn re- I leased closing" itsback contacts-and the relays i 1,

19; 25; 5D andifiare 'governed-insubstantially the same manner'as-whenrelay-St is released; That is; theclosingnof back-contactslil, (58,69 and 82 .;otrelay 5l completes circuits for relays i9; 16;

fiend-H; respectively. It follows that an emer gency: alarmis provided for nearby trains when the-train 'of which caboose CO -is-a part is deceleratingas m-aybe-caused-by an emergency" brake application.

automatic -device PS- and the generator 55 provide automatic control of the emergency "alarm signal in response to braking conditions. It-is apparent that either one of the two devices may be used alone, or thetw'o may be used-as an extra precaution; Furthermore, it is apparent that the relay 39hr the relay 56' can be'gove'rned through a hot journal bearing det'ctorb'r some'other part .of"th'e"train"and 'th'usprovide emergency alarm 'foi 'other conditions ofth'e train.

Also,

It-is to be observed that as here illustrated the corresponding paths governed by the relays 30 and 51, as will be readily understood by an inspection of the drawing.

Thus operation of the switch EM causes the transmitter TR to alternately supply the two emergency alarm currents for sending an emergency alarm to all nearby trains and wayside stations. The switch EM would be used by a member of the crew in the caboose CO who might observe some hazardous condition either on his own train or on some other nearby train or some condition along the trackway.

It is to be seen, therefore, that the apparatus disclosed in the drawing is effective for sending a distinctive emergency alarm current when a hazard occurs, and which alarm current is effective to create on all trains in the vicinity of such hazard a distinctive alarm, causing the crews of these trains to be on the alert to take such action as may be required to bring their trains under control.

Although I have herein shown and described but one form of railway train emergency alarm apparatus embodying my invention, it is understood that various changes and modifications may be made therein within the scope of the appended claims without departing from the spirit and scope of my invention.

Having thus described my invention, what I claim is:

1. In combination, a railway train vehicle having mounted thereon transmitting apparatus operable to supply either a first or a second current of different preselected carrier frequencies, generating means operable to supply oscillations of either a first or a second preselected tone frequency, said generating means connected to said transmitting apparatus to modulate the first and second carrier frequency current by said first and second tone frequencies respectively to sup ply a first and a second alarm current, control means having contacts to govern the conditioning of said transmitting apparatus and said generating means to alternately supply said first and second alarm currents in a cyclic manner, and means including a contact member connected to a given element of said vehicle to automatically govern said control means when a predetermined operating condition occurs.

2. In combination, a railway train vehicle having mounted thereon transmitting apparatus operable to supply either a first or a second current of different preselected carrier frequencies, generating means operable to supply oscillations of either a first or a second preselected tone frequency, said generating means connected to said transmitting apparatus to modulate the first and second carrier frequency current by said first and second tone frequencies respectively to supply a first and a second alarm current, control means having contacts to govern the conditioning of said transmitting apparatus and said gen. erating means to alternately supply said first and second alarm currents in a cyclic manner, and means including a contact member actuated by the brake pipe pressure of said vehicle to govern said control means for supplying said alarm currents when a predetermined brake application is made.

3. In combination, a railway train vehicle having mounted thereon transmitting apparatus operable to supply either a first or a second current of different pre-selected carrier frequencies, generating means operable to supply oscillations of either a first or a second preselected tone frequency, said generating means connected to said transmitting apparatus to modulate the first and second carrier frequency current by said first and second tone frequencies respectively to supply a first and a second alarm current, control means having contacts to govern the conditioning of said transmitting apparatus and said gen erating means to alternately supply said first and second alarm currents in a cyclic manner, a generator connected to an axle of said vehicle to generate a voltage due to the speed of rotation of the axle, a relay connected to said generator to be eifectively energized in response to a given rate of change in the generated voltage due to a predetermined change of the speed of rotation of the axle, and circuit means controlled by said relay to govern said control means.

4. In combination, a railway station having telephone equipment using either a first Or a second carrier frequency for telephone communication with trains within a given range of the station through a transmitting circuit common to all the trains, an electron tube oscillator at said station, control relay means to govern the transmitting portion of the telephone equipment at the station to select the carrier frequency to be supplied and to connect at times said oscillator to the transmitting portion for modulating the carrier by the generated oscillations, a circuit controlling contact at said station to be operated in response to a predetermined hazard, and means including said circuit controlling contact to automatically govern said control relay means to condition said transmitting portion and said oscillator to supply said first and second carrier frequency alternately in a cyclic manner and modulated by a first and a second tone oscillation to sound through the receiving portion of the telephone equipment of each train within said range an alarm of the occurrence of said hazard.

5. In combination, a railway station having telephone equipment using either a first or a second carrier frequency for telephone communication with trains within a given range of the station through a transmitting circuit common to all the trains, an electron tube oscillator at said station, a first control relay to govern the transmitting portion of the telephone equipment at the station to select the carrier frequency to be supplied, a second control relay to connect at times said oscillator to the transmitting portion to modulate the carrier supplied, a third control relay to govern said oscillator to generate either a first or a second tone frequency, a circuit controlling contact at said station automatically operated when a given hazard occurs, and means including said circuit controlling contact to govern said first, second and third control relays as required to condition the transmitting portion and said oscillator for supplying said first and second carrier frequencies alternately in a cyclic manner and modulated by a first and a second tone frequency respectively to sound through the receiving portion of the telephone equipment of each train within said range an alarm of the occurrence of said hazard.

6. In an emergency alarm means for use with a railway train telephone equipment using a carrier frequency current for telephone communication with remote stations having similar telephone equipments, the combination comprising, alarm current supply means on said train operable when energized to create oscillations of a preselected tone frequency and having connections to the transmitter portion of the train telephone equipheteleph s uir m Ma d- Jnen to modul e the carr er tcurr r n '-b $fi. l v le i 2n tQ-provi mn;etmersencytalarmac re @w r i v in ermetin nev q ic id ai :qp fiableiwhen efituetsdrt i ecurrsntlv at W eidp p llat ns-t pro id muses-fi h w ia n ml rm; Q ment'tq aew ml fi a ala m s thmi zth l-V6 1291;, v

r. r creme-t tationer lm mbwnz si train:ppereti elvzeo i td i r i lem n .wuete-tb @ente ply a carrier current, of .a preselected frequency,

train carried generating means operablefto supply. oscillations ofua preselected frequency cliaraci i s d 'er e in mean in :Qn scti0n to "51am Y transmitter v to mp duiate, said carrier (by rl e s q i to b v ii 7 an emer en lar w re a 'v il errr m r qn a l r c e tl actuate onta t q ntac membe operably associategi withjen elementpf. said train to actuate th mm .membe x i es pss ton i n m ha rdous Q0Bdi 91 an c nt jm in ll s fl sa d interr ter ntact d ai e ei lrhav n mo t req --a=tmnsm. t per bl t e-we nta@ memb t overn saidg neratinemeans t c re u n cr ate sa dco qil at o o p o i recurrent pulses of saigt merg encxalarmcurrent. n "comb nation :a. ra wa trai having w unt there pt ransm tt op r b es pm arca rie ourrsn iO .-;-a:pree1e f qu n y, traincarriedgenerating means operable to supply sc lat .o a s le tedireque cy chara li s i. vsaid z enqr n means havi n itions to said transmitter: to modulate said carrier -by-said oscillations-to provide an-emergency alarm current, a circuit interrupter; operable to recur- I lt yaCt1late a coptac a; con act. mem p nativhely :connectedrto anelement of said train to actuate the contact -member-in response to .a given-train hazardous condition, and control means: including said-interrupter contact and said contact member to recurrently interrupt said ..emergenc.y alarm lcurrent.

LABS O. GRONDAHL.

Number 

